The process of the present invention relates to a "post-press" or second press molding operation for molding a fiberboard into a desired shape while, at the same time, creating thick, hard, integral surface portions on the surfaces of a man-made fiberboard substrate. The fiberboard substrate is formed by consolidating a mass of fibers. This may be done by either the dry process or the wet process method of manufacturing fiberboard. Typical products made by these systems are medium density fiberboard and insulation board. The board is thereafter "post-pressed" in a mold having a desired configuration, to form the consolidated fiberboard into a desired shape, to impart surface texture and to form dense surface layers while retaining a lower density core or central portion of the fiberboard. For the purpose of the present invention, a "post-press molding" operation refers to a molding step performed on a consolidated fiberboard which changes the dimensions of the consolidated fiberboard in at least two dimensions.
It is necessary to form the furniture part of the present invention in two separate operations. The first operation forms a consolidated fiberboard common in the art of forming a fiberboard, such as insulation board. The second step comprises "post-press molding" which changes the dimensions of the consolidated fiberboard in at least two dimensions to correspond to the dimensions of the mold, and creates denser surface portions on the fiberboard. It is quite surprising that a "post-press molding" operation is effective in substantially altering the dimensions of the consolidated fiberboard and in densifying the surfaces of the consolidated fiberboard.
It is very difficult to both densify and restructure the surfaces of a consolidated fiberboard without destroying the fiber-to-fiber surface welds referred to in our co-pending application Ser. No. 739,184, filed Nov. 5, 1976. In accordance with the present invention, it has been found that the configuration, surface density, and physical characteristics of a completely consolidated fiberboard mat can be altered in a post-press molding operation when at least the surface fibers of the mat are contacted with urea prior to the molding. During the post-press molding operation, at a temperature of at least 525.degree. F., the urea reacts to stiffen and strengthen the surface layers of a low density cellulosic fiberboard substrate, defined herein as fiberboard having a density in the range of 10-35 pounds/cubic foot, to provide the strength necessary for the product to be useful as a furniture part while, at the same time, restructuring the board to a desired configuration. The resulting lightweight product has a look, feel and sound equivalent to that of natural wood, while being produced at a much lower cost.